Qock reading altimeter



Dec. 13, 19 38. KOLLSMVAN Re. 20,948

QUICK READ ING ALTIMETER Original Filed Dec. 10, 1931 4 Sheets-Sheet 1 FI 1 INVENTO-R l HUL KDLLSMFIN ATTORNEY P. KOLLSMAN QUI CK READINGALTIMETER Dec. 13, 1938.

Original Filed Dec. 10, 1931 4 Sheets-Sheet 2 INVENTOR 1 fgHUL KOLLSNHNATTm Dec. 13, 1938. P. KOLLSMAN QUICK READING ALTIMETER Original FiledDec. 10, 19

31 4 Sheets-Sheet 3 Dec. 13, 1938. KOLLSMAN- Re. 20,948

QUICKREADING ALTIMETER Original Filed Dec. 10, 1931 4 Sheets-Sheet 4FIG-.6

INVENTOR 5PM. KOLLSNHN ATTORNEY til Reiscued Dec. 13, 1938 QUICK BEADlJWG ALTIMETEB Paul Kollsman, New York, N. Y.

Original No. 1,857,311, dated May 10, 1932, Serial No. 580,119, December10, 1931. Reissue application October 27, 1932, Serial N0. 639,897.

vided and this application for reissue January 8, 1934, Serial No.105,642

IClaim.

This application is a division of my copending application Serial No.639,897, for the reissue of my Patent No. 1,857,311, said applicationhaving been filed on October 27, 1932.

This invention relates to indicators and more particularly to aneroidaltimeters. A quicker'and more dependable understanding of the objectsof the invention will be had by referring first superficially to thestructure by reference character. The outer stationary casing I2 is ahousing for mounting the whole altimeter in an instrument panel. Anywell-known type of aneroid or barometric pressure responsive mechanismincluded in the aneroid means ll operatively connects with and rotatesthe spindle 45 of large pointer 43 in response to changes in barometricpressure.

interior of itsenclosing sub-casing. This front plate I8 is made fast tothe sub-casing of the aneroid means II and is in the form of a gear bywhich the aneroid means is'rotatedly adjustable relatively to thestationary.casing I! by a setting means,

The parts visible through the glass lll broadly speaking are indicatingmeans or elements. In this broad class are included pointer means,pointer elements or pointers such as the pointers 43 and 44, whichpreferably constitute all of the indicating means which is moved by thepower of the aneroid means. Also included under the broad definitionindicating meansare the dial means or scale means such as the dial 32:Likewise broadly included under the term indicatlng means are thereference means, reference elements, or reference marker such as thereference elements 36, and 21, although the reference element 21 isshown in the form of a rotatable member bearing a series of indicatingreference numbers.

Setting means manually operable by the knurled knob 53 functions toeffect relative setting movements or adjustments involving some orall ofthe indicating means and, if desired,

' the aneroid means. This setting movement, af-

fected by the setting means, is in contradlstinction-to the operativemovements of the pointer means by" the aneroid mechanism of aneroidmeans ll-altitude responsive means.

This specification most particularly relates to features which makepossible the rapid reading of an indication regardless of whether .theindication to be read is in response to the actuation of an aneroidmeans usually employed in connection with altlmete'rs, or to actuatingmeans Spindle 45 passes freely through thefront plate It of the aneroidmeans ll into the v usual for tachometers, or to indicators for stress,flow, air speed, and the like. More particularly, the object "of theinvention is to provide for the instantaneous reading in the decimalsystem without calculation of any kind and through the medium of atleast two dissimilar pointers.

A further particular object of the invention is to simplify and speed upthe reading of an indicating instrument over a wide range. To this end Iprovide a dial having a single scale divided uniformly from one to ten,cooperating with two unlike pointers concentric with the said scale andoperating in response to the aneroid means in proportion to changes inbarometric pressure in the ratio of one to ten, with their zeropositions corresponding to the zero on the single scale. By thisarrangement, in carrying out this object of my invention, the completerotation of one pointer may represent a thousand foot change inaltitude, which is indicated by the other pointer by one major divisionon the scale.

A large pointer may be a high speed pointer and a shorter pointer a lowspeed pointer. If the short pointer indicates somewhere between 2 and '3on the single scale, and the long 25 pointer indicates ,5, a glance atthe pointers on the single scale instantly indicates 2500 feet withoutany cooperative calculation. This indicating means instantly indicatesaltitude in strict accordance with the decimal system with all theaccuracy of a sensitive pointer and all the necessary range of a slowmotion pointer.

A further object of the invention is to provide suitable interconnectinggearing and setting means for setting such pointers having a ten to oneratio to accord with the setting of a reference element, preferably toany indication throughout the entire practical range of flying, and soas to accord with my heretofore mentioned object of causing the sum ofsetting changes to equal zero.

The above and further objects of the inven--- tion will beparticularized more fully in the following claim, which is directed toillustrative embodiments of the invention described in the followingspecification in connection with the adcompanying drawings for purposesof illustration, and not limitation.

In the drawings Fig. 1 is an enlarged vertical section through thealtimeter at right angles to its normal position on the instrumentboard, with 0 part broken away at the locality of the aneroid means;Fig. 2 is a section atright angles to the section of Fig. 1 through theplane or line 2-2; Fig. 3 is a front elevation of the altimeter with,

one embodiment for the indicatingmeans lndi- I cating the elevation of1340 feet relatively to sea level; Fig. 4 is a view similar to Fig. 3 ofthe same instrument set for landing on a landing field with elevation ofthe altimeter of my invention with the indicating means set for levelflight at 940 feet net and subsequent landing upon a landing field withthe elevation of 400 feet above sea level.

The embodiment of the indicator shown is an altimeter III of the typeactuated by an atmospheric pressure sensitive means, shown in the formof any approved aneroid means ll the entire mechanism of which ispreferably housed within a cylindrical shell or subcasing mountedpreferably concentrically within the stationary casing l2 adapted to befixedly mounted in the instrument panel in the position indicated in thefigures.

Broadly speaking, such aneroid means provides a yielding elementoperated by a varying force.

The entire aneroid means isshown mounted for manual adjustablerotation... A hub l3, suitably fixed -to and axially of the stationarycasing I2, journals a stub shaft l4 fixed to the subcasing of theaneroid means II, and is shown retained by a screw l5. The front of theaneroid means is closed by a front plate l3 fixed thereto and shown inthe form of a gear. This gear l8 has a circular recess ll affordingrotary bearing engagement on an angular portion ll of housing l2. Byreason of this angular formation I! an annular enlargement I9 isafforded for receiving the toothed part of the gear l6 and other partspresently to be described.

Associated with and in front of the gear I 8 is a gear 29, which isshown tobe concentric with and of equal diameter with the gear l6 and,

under certain conditions, may be rotatable relatively thereto. This gear20 may be mounted in a suitable manner. It is formed integral with a hub22 bearing in the circular recess 2| formed concentrically with the gearl8. The cylindrical hub 22 has a front wall -or closure 23, serving as amount for other parts presently to be described. i

Journaled externally on the cylindrical hub 22 is a gear 24 in front ofthe gear l8 and between it and the gear 29, but spaced apart therefrom asufiicient amount to accommodate the gear 25 of smaller diameter andmade fastthereto in any suitable manner, as byscrews. This gear 25 is ofsmaller diameter than gears I8, 20, and

24 and is determined by a gear ratio presently to be ,described.

Also journaled on the exterior of cylindrical hub 22, but on the frontside of gear 29, is a gear 26 of smaller diameter. This gear 25functions to carry a reference means such as the ring shaped numeralbearing rotary member 21.

The rotary reference member 21 beats numerals in graduated orderindicating barometric pressures as they rotate into visibility throughwindow 33. The reference member 21 may rotate freely 360 or more andits, rotation is not limited by any stops. Interconnecting the gears 25and 25 is a gear train including pinions 28 and 29, both'fixed t0 thesame stub shaft 30 concentric. therewith and thereby journaled in aperforation through'gear 20. These gears 23 and 29 are positioned onopposite sides of gear.2ll (28 in the rear thereof and 29 in frontthereof). The pinion 28 engages gear.25 and pinion 29 may engage a gear3|, journaled on the web of gear 20' and gear 3| is shown in turnengaging the gear, whereby various relative rotations may be caused totake place, in accordance with any one of various manual manipulationsof a setting means presently to be described.

A dial 32 is fixed relatively to gear 20 by being mounted fixedly to thefront closure 23 of hub 22. This dial 32 has a window 33, through whichvarious reference elements ormarks such as numbers indicating variousbarometric pressures in inches of mercury and fractions thereof may beobserved. By reason of the fact that the rotatable member of cylindrical,or ringshaped dial 21 is capable of a complete ir'otation, relativelygenerous spacing may be employed, even though the entire range ofbarometric pressure, throughout which range it may be desired to make areference setting, is employed and numerically designated on thisrotatable member 21.

It should be noted that none of the gears I5, 24, 20, nor 35, about tobe (imcn'bed, are operated by the aneroid means i I. They are operablesolely in response to the manual manipulation of the setting means and,as indicated particularly in Figs. 1 and 2, rest in the annularenlargement l9 of the stationary casing I2 in frictional engagementtherewith, which frictional engagement is at their extreme periphery,the mass of the parts tending to hold them in fixed position relativelyto the fixed casing "I2 until and unless they are manually adjusted bythe setting means presently to be described.

For rotating the gear 35 carrying the reference altimeter has as itspointer means, along pointer 43 and a short pointer 44, which arerelatively rotatable in predetermined different degrees by the aneroidmeans II, which operates through any well known connecting mechanism torotate the spindle equal angular amounts in proportion to equal changesin feet altitude. The spindle 45 extends freely through the front plateor gear I 8 and through the hollow shaft or rotatable hub 45,journaledin an opening in wall 23 and dial 32 for Figs. 1, 2, 3, 4, 5,and 6.

' The long or sensitive pointer 43 is secured on spindle 45, and theshort or range pointer 44 is carried" by the hollow shaft 48.Interconnecting shafts 45 and .45 is a planetary gear train. A gear orpinion 41 is fast to the spindle 45 and meshes with gear 48. Pinion 49is fixed to the same shaft as is gear 48, which shaft is journaled tothe cylindrical hub 22, 23, which is integral with the gear 29. Pinion49 meshes with gear fixed -'to the hollow shaft 48 and serving to drivethe range pointer 44 at any desired ratio relatively to pointer 43,preferably at the angular speed ratio of one to ten. At this point itshould be noted that it is the rotatability of the cylindrical hub' 22,23 which mounts-the shaft of gear and pinion 48 and 49 which constitutesthe sun and planet relation in this gearing, the advantage of .which winlater be described.

w ns

The manually operable setting means is mounted in an extension of thecircular casing enlargement iii. A shaft 52 slidably extends from frontto rear through this enlargement 5| and has fixed thereto a pinion 54which, together with the shaft 52, is urged rearwardly by thecompression spring 55, preferably seated in a pocket. A removable setscrew 56 secured in the rear end of shaft 52 serves as a removablelocking means limiting the setting operation of the pinion 54. Bysuitable manipulations of the setting means, various combinations of thegears I5, 24, and 20 may be operated by means of the pinion 54. With thesafety locking screw 55 in place, only two combinations may be operated.With the parts positioned as shown in Figs. 1 and 2, a. simple rotationof the knob 53 drives both gears l5 and 24, while gear 20 is heldstationary relatively to the casing [2 in any suitable manner, as by itsfrictional engagement therewith. This setting combination or PositionNo. 1.

With the apparatus as shown in Fig. 1, by pulling out on the knob 53 andturning it, pinion 54 is caused to engage all three gears l5,-24, and25, to effect a simultaneous rotation of'said three gears. This iscombination or Position No. 2.

If the safety locking screw 55 is removed, and the knob53 is pulledforward slightly farther than for position No. 2, pinion 54 may becaused to engage solely gears 24.and 20, whereupon a rotation of theknob 53 rotates said gears 24 and 25, while gear I5 is held stationaryrelatively to casing I2, as by its frictional engagement therewith. Thisis combination or Position No. 3.

If the knob 53 is pulled still farther forward, pinion 54 will be causedto mesh solely with gear 20, whereupon a rotation of knob 53 rotatesgear 2!], gears l5 and 24 being held stationary in any suitable manner,as by reason of their frictional engagement with the stationary casingl2. This is combination or Position No. 4.

Operation With the parts in the position shown in Fig. 1, a rotation ofshaft 52 and its pinion 54 clockwise as shown in Fig. 2, a manualsetting of the altimeter may be effected with reference to a particularcondition, such as the foot altitude of a landing field, the barometricpressure at a landing field, the foot altitude desired for level flight,or the barometric pressure corresponding to desired level flight.(position No. 1), the pointers 43 and 44 and the reference element 35,all three relatively to the scale means upon which they read, are causedto change thier indications so that the sum of the changes is equal tozero and therefore equal to a constant. Likewise a relative changebetween the numerical barometric pressure indications of the rotatablereference element 21 is to be made so that the sum of its change plusthe change of the pointer means is also equal to a constant and to zeroin the same unit of measure.

By reason of the fact that the rotary members 21 and 25 are not limitedin their rotation but are free to rotate a complete rotation of 360 andmore, substantially nolimits are imposed upon the gear train includinggears 25, 25, 29, 3| and 25, which gear train determines the angularrate of rotation for the member 21 relatively to other rotary parts suchas the fast pointer 43 and the slow pointer 44. From the drawings it maybe determined approximately what this relative angular rate of rotationis.- The gear ratio between In making this manual setting gears 29 and3| is shown to be approximately 5 to 1 while the ratio of gear 25 togear 25 through their interconnecting gears 28 and 3| is approximately 8to 7. The complete gear train therefore gives an angular speed to therotary member 21 relatively to gear 25 and gear 24 of 7 to 40. The rateof rotation of fast'pointer 43 is unity or one. As previously describedthe rate of rotation of slow pointer 44 is one-tenth. Therefore, in theshowing of the drawings rotary member 21 rotates slower than the fastpointer 43 and faster than the slow pointer44, sevenfortieths being lessthan one and more than onetenth.

Position No. 1

Fig. 3 shows a position of the indicating means indicating an altitudeof 1340 feet, which is indicated by the pointers 43 and 44 on scale 31relatively to zero altitude or sea level, as indicated by the nearestcorresponding number for normal sea level barometric pressure. Assumethat it is now desired to set the altimeter for landing upon a landingfield with the elevation 400 feet. By telephone communication with thelanding field, the foot altitude of the landing field, 400 feet, may beobtained or the corresponding barometric pressure, 29.5, may beobtained.

If the foot altitude is obtained, a clockwise rotation of knob 53, asviewed in Figs. 3, 4, and 5,

serves to move the reference marker to indicate 400 feet, as shownin'Fig. 4. The gearing intergearing rotatable reference element 21causes this element to indicate the barometric pressure 29.5corresponding to 400 feet. In likemanner, if the barometric pressure ofthe landing fleld and not its foot altitude is obtained, the sameclockwise rotation of knob 53 is imparted until the barometricpressure29.5 is indicated through window 33, whereupon the corresponding footaltitude will be indicated by the reference marker 35 upon the scale 31.

Now, at the same time that these reference elements 36 and 21 are beingset to correspond with the landing field condition, the pointer means ismoved counterclockwise or in a negative manner to subtract 400-feetaltitude from its indication in Fig. 3, so that in Fig. 4 it correctlyindicates 940 feet, the distance above the landing field, so that thepointer means will indicate zero when the level of the landing field isreached.

It is thus clear that the sum of the negative change of the pointermeans relatively to its scale 31 andthe positive change of the referencemeans 35 relatively to the same scale 31 is numerically zero, andtherefore equal to a constant. In like manner, by altering thebarometric pressure change from the showing that corresponded to sealevel to that corresponding to the atmospheric pressure at the landingfield into feet altitude,

again the changes are equal to zero.

Position No. 2

It may be desired to continue flying at level flight at the altitude of1340 feet. To facilitate this, with the parts in position No. 2, arotation zont'alof pointer 43 and any change below level flight isindicated by a movement of pointer 43 below horizontal. This is a moreconvenient telltale than the necessity of reading pointer movement froma position such as that shown in Fig. 3.

In Fig. 6, pointers 43 and 44 are inter-geared in the ratio of ten toone. Each individually indicates 940 feet altitude with the pointer 43horizontal, so that an upward movement of pointer 43 indicates a rise ofthe plane above, and a downward movement of this pointer indicates adownward deviation from the same indication for level flight.

Position No. 1Gear movement .A clockwise rotation of knob 53, assumingthe aneroid indication to be as shown in Fig. 3, is imparted untileither the reference marker 36 indicates the desired reference conditionor' the rotatable reference element 21 indicates the desired.referencecondition. The gear functioning to effect this setting is as follows:Gear 26 is held fast by any suitable provision such as friction.Counter-clockwise rotation is imparted to gears I 6 and 24. Gear 25,fixed to gear.24, rotates counter-clockwise and imparts clockwiserotation to gears 26 and 26 and 42. Gear 26 imparts counter-clockwiserotation to gear 3| and gear 3|, in mesh with gear 26, imparts clockwiserotationthereto. The gear ratio of the train and the numeral marking aredesigned to transform feet altitude into barometric pressure in inchesof mercury for rotary reference element 21, and one twentieth of footaltitude indication for reference marker 36 relatively to the angularmovement of pointer 43.

The clockwise rotation of gear 42 meshing with internal gear impartsclockwise rotation to gear 35 and the reference marker 36 carriedthereby. The gear train operating reference marker 36 is designed toimpart the same angular movement to reference marker 36 as that impartedto gear l6 operating pointer 44 from spindle 45, a commen-.

surate ten to one reduced negative movement is imparted to pointer 44 inperfect synchronized accuracy. At the same time that the settingadjustment is being made, there is no interference with the operativefunctioning of the aneroid means ll upon the pointers 43 and 44 throughthe spindle 45.

' Position No. -2Gear functioning By reason of the fact that the pinion54 simultaneously engages the teeth of gears I6, 24, and 26, no movementof gear 42 on its shaft 36 is possible, so that it serves as aflxedgripper for internal gear 35, causing internal gear 35 with itsreference marker 36, as .well as the aneroid means, pointers and scales,and, in fact, all the indicating means, to move as an entirety from theposition shown in Fig. 3, for example, into the position shown in Fig.5. This setting movement is effected also without interfering, duringits progress or after its completion, with the operative functionin ofaneroid means ll.

Position No. 3Gear functioning In Position No. 3, pinion 54 engagessolely gears 24 and 26, gear I6 with the rest of the aneroid means beingsuitably held in fixed position as by gictlignal engagement with thestationary cas Gears 24 and 26, being relatively non-rotatable by reasonof the simultaneous engagement of their teeth by pinion 54, prevent anyrotation of gears 26, 26, and 42 about their axis 36, although they dorevolve about the major axis passing through spindle 45 in the angularamount that rotation is imparted to gears 24 and 26. Pinion 26 holdsgear 3| against rotation on its axis, although it revolves about thecentral axis and acts as a gripper for gear 26 carrying the referenceelement 21. Likewise, the non-rotating gear 42 serves as a gripper forthe internal ,gear 35 carrying reference marker 36. An adjusting settingmovement is therefore imparted to reference elements 21 and 36 and dial32.

In addition, the rotation of the planetary mounting 22, 23 carrying theshaft of gears 46 and 49 imparts an adjusting movement to pointer I 44relatively to pointer 43, then stationary by reason of the fact that theaneroid means I I with its spindle 45 is then stationary, provided theratio of gear 41 to gear 46 is unequal-to the ratio of gear 56 to thepinion 49. Obviously, if such-ratios are identical, the planet gearswould roll about the two sun gears 41 and 56 without causing anyrelative rotation between the gear 56 and the gear 41. Such, however, isnot the case and the corrective adjustment is efiectable by reason ofthis planetary gear arrangement. ing movement may be effected in eitherangular direction to impart a relative corrective setting for theelements of the indicating means just enumerated.

Position No. 4Gear functioning It is assumed that the indication of thealtim eter is the same as that described for Position No. 1 gearmovement, namely, as is shown in Fig. 3,

- indicating an elevation above sea level of 1,340

feet, and that it is desired to set the altimeter for landing upon alanding field with an elevation bf 400 feet above sea level so as toobtain an indication like that shown in Fig. 4.

To effect this setting of the altimeter as was described in connectionwith Position No. 1, a clockwise rotation was imparted to the fingerknob 53. For accomplishing it in this other way, namely that of PositionNo. 4, a counter-clockwise rotation is imparted to knob 53 and inconsequence, a counter-clockwise rotation of pinion 54 results.

functioning as a planetary journaling for the multiple gear unit 26, 23,and 42 on the same shaft 36, large gears l6 and 24 being held stationaryin a suitable manner by reason of their frictional engagement with thestationary casing 12 at 'the portion 16. Gear 26 functioning as a planetgear about central axis 45 and in toothed engagement with the thenstationary gear 25 is caused to rotate about its axis 36 in a clockwisedirection, and also gears 23 and 42 forming a unit with gear 26. Gear 23in mesh with gear 3| drives gear 3| counter-clockwise. Gear 3| rotatingcounter-clockwise in turn drives gear 26 clockwise, and gear '26,carrying the rotary reference member 21,-imparts a clockwise settingadj'usting movement to the rotary member 21. During this, rotation ofthe reference member 21 This adjust- The counter-clockwise rotation ofpin .ion 54 causes a clockwise rotation of gear 26, now

stationary positioning of the aneroid means H but dial 32 with its scale31 has been rotated clockwise relatively to casing l2, just the angularamount that gear 20 has been rotated, by reason of the fact that it issecured on the hub 22, 23 of this gear 20. of the dial 32 does notinterfere with the setting of the reference marker 36 on scale 31 ofdial 32 so as to indicate the 400 foot elevation 01' the landing field,by reason of the fact that the reference marker 35 is caused by this sunand planet arrangement to travel angularly at twice the angular raterelatively to casing l2 of the rate at which the dial 32 is rotated andlikewiseclockwise. The proper setting is indicated on the instrument assoon as the reference marker 36 coincides with the major marking 40 ofscale 31, although for this second method of setting, the scaleindication 4 no longer occupies the position shown in Fig. 4, but hastraveled around to the angular position indicated in Fig. 4 by theposition of the mark 8 and the zero of scale 31 has been caused tooccupy the position of the mark 4 as shown in Fig. 4. By thisfunctioning, the negative setting of the pointer 43 relatively to thescale 31 is accomplished by moving the scale 31 negatively relatively tothe stationary pointer 43 instead of moving the pointer 43 negativelywith relation to the scale. This setting adjustment in accordance withPosition No. 4 not only fixes the position of the reference marker buthas caused the pointer 43 to indicate 940 on scale 31.

The clockwise rotation of rotary reference member 21 has now caused anumerical indication of the barometric pressure corresponding to the 400foot altitude of the landing field to be displayed through window 33. Itis to be understood, therefore, that this No. 4 position setting can beeffected by rotating the knob 53 counterclockwise until the properbarometric pressure corresponding to that at the landing field isindicated through the window 33, provided it is barometric pressure thatwas obtained as by telephone communication with the landing fieldinstead of foot altitude. Foot altitude makes it convenient to adjustthe reference marker 36, whereas barometric pressure at the landingfield makes it convenient to set by means of the numeral bearingreference marker 21 shown through window 33.

So far, there'has been described the proper relative setting betweenscale 31, pointer 43, reference marker 36, and reference marker 21. Anadvantage of this invention in connection with pointer 44 is alsopresent.

The rotation of gear clockwise the equivalent of four major divisions ondial 32 revolves the common planet shaft of gears 48 and 49 clockwise anequal angular amount. By reason of the ten to one ratio in the geartrain 41, 48, 49, and 50, this sun and planet functioning effects acounter-clockwise rotation of the short pointer 44 one-tenth of therelative rotation between dial 32 and the long stationary pointer 43, soas to cause it to indicate the nine-tenths or less than unit indicationon scale 31. Thus it is to be seen I adjustment exactly as they indicaterelatively to However, this clockwise rotation the scale :1 in Fig, 4.Now, if desired, the knob v53 may be manipulated in Position No. 2 torotate the entire indicating apparatus and aneroid so as to cause anindication exactly as is shown in Fig. 4.

There has now been described the complete functioning through the mediumof Position No. 4 to effect a setting as is indicated in Fig. 4.Obviously, such could not be the case if the shaft for gears 48 and 49was fixed relatively to the casing I2 or relatively to the aneroid meansII. For the ten to one ratio between pointers 43 and 44, gear 48 dividedby gear 41 times gear 50 divided by gear 49 should equal ten.

This setting of the indicating and reference means by moving solely thegear 20 with gears l6 and 24 stationary is therefore the converse orreverse of the action when gears I6 and 24 are rotated and gear 20 isheld stationary. Stated difierently, this Position No. 4 functioningmoves the dial 32 relatively to a stationary casing and a stationarypointer 43 and gives a compensating movement for the range pointer 44and allows the aneroid means II to be stationary relatively to thecasing l2 while the reference means 35 and 21 are properly set also.

The advantages of the invention as above out lined are best realizedwhenall of its features and instrumentalities are combined in one and thesame structure, but useful devices may be produced embodying less thanthe whole. It will be obvious to those skilled in the art to which thisinvention appertains, that the same may be incorporated in severaldifferent constructions. The embodiment shown and described herein,therefore, is submitted merely as showing a preferred exemplification ofthe invention. While the invention is applicable to altimeters, it isalso applicable as to many of its sub-combination elements, totachometers, and indicators for stress, flow, air speed, and the like.For example, the housing of all the parts in a single casing providing aclearly visible dial with a large peripheral scale indicating in thedecimal system from a plurality of pointers, may have advantage in theconstruction of many indicators. The pointers 43 and 44. are shownhaving counter balancing extensions 43' and 44'. This provision, inaddition to the simple type of intergearing of these pointers, tends tomake the entire indicator serviceable regardless of the'direction andamount of gravitational force or its equivalent, combined gravitationaland centrifugal force so often present in air-plane service.

It will be appreciated that various changes and modifications may bemade in the device as shown in the drawings, and that the same issubmitted in an illustrating and not in a limiting sense, the scope ofthe invention beingvdefined in the following claim.

I claim:

An altimeter having a scale, an indicator, a

plurality of pointers movable in the ratio of one to ten by theindicator, said pointers being coordinated with said scale, and theindicator and scale being rotatable relatively to each other.

PAUL KOLLSMAN.

